"Heavy winds and torrential rain has caused damage to the area's electricity infrastructure and Wellington Electricity is working quickly and safely to restore power supply, however, the increased volumes of work and weather conditions could cause some delays in restoration," a Wellington Electricity spokesman said.

People should stay away from fallen power lines and trees, listen out for official advice, and check on elderly neighbours.

"Above all please be patient and spare a thought for power company crews, who are working safely and rapidly, often under harsh conditions, to restore your service."

Wellington Civil Defence controller Bruce Pepperell said it was expected power would be returned today to 17,000 of the affacted homes, but for up to 5000 homes the power outage might last another night.

He said it was not yet known which suburbs might remain off the grid, but updates would be provided as soon as the information was available.

Powerco also reported power outages around the lower North Island.

Powerco reported this morning about 2,800 customers were without supply in lower North Island, including 600 homes in Wairarapa and 200 in Taranaki.

Reports of fallen or damaged power lines can be called into your local council, who are coordinating with electricity providers to work through a significant number of repairs.